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United States Patent |
5,284,421
|
Chlus
,   et al.
|
February 8, 1994
|
Rotor blade with platform support and damper positioning means
Abstract
A rotor blade having axially spaced gussets disposed between a root portion
and a platform is disclosed. Various construction details are developed
which provide a gusset providing both platform support and damper
positioning means. In one particular embodiment, a rotor blade assembly
includes a plurality of circumferentially spaced rotor blades having
dampers disposed between adjacent blades, wherein each blade includes an
axially spaced pair of gussets extending laterally from the rotor blade.
The gussets extend from a root portion of the rotor blade to a platform
and provide radial support of the platform during rotation of the rotor
assembly. The gussets include a curved lateral edge which, during rotation
of the rotor assembly, urges the damper away from the root portion of the
blade.
Inventors:
|
Chlus; Wieslaw A. (Wethersfield, CT);
Houston; David P. (Glastonbury, CT)
|
Assignee:
|
United Technologies Corporation (Hartford, CT)
|
Appl. No.:
|
980848 |
Filed:
|
November 24, 1992 |
Current U.S. Class: |
416/248; 416/500 |
Intern'l Class: |
F01D 005/10 |
Field of Search: |
416/248,500
|
References Cited
U.S. Patent Documents
3666376 | May., 1972 | Damlis | 416/500.
|
3887298 | Jun., 1975 | Hess et al. | 416/500.
|
4101245 | Jul., 1978 | Hess et al. | 416/500.
|
4182598 | Jan., 1980 | Nelson | 416/500.
|
4455122 | Jun., 1984 | Schwarzmann et al. | 416/190.
|
5228835 | Jul., 1993 | Chlus | 416/500.
|
Primary Examiner: Kwon; John T.
Claims
What is claimed is:
1. A blade assembly for an axial flow turbine engine, the turbine engine
having an annular flow path disposed about a longitudinal axis, the blade
assembly adapted to rotate about the longitudinal axis during operation of
the turbine engine, the blade assembly including:
a plurality of blades circumferentially spaced about the longitudinal axis,
each blade including an airfoil portion, a platform, and a root portion,
the airfoil portion extending through the flow path and having a pressure
surface and a suction surface, the platform disposed radially inward of
the airfoil portion, extending laterally about the blade, and including a
radially inward facing surface, the root portion disposed radially inward
of the platform and the airfoil portion, the root portion having a neck
disposed at the radially outward end of the root portion, the neck
including a pressure surface side and a pair of gussets axially spaced and
extending from the pressure surface side of the neck, each gusset
extending from the neck to the radially inward facing surface of the
platform and having a lateral surface with a radius of curvature R.sub.1
at the juncture of the gusset and the platform, the gussets adapted to
provide radial support of the pressure side platform during rotation of
the blade assembly; and
a plurality of dampers, each damper disposed circumferentially between
adjacent root portions, engaged with the radially inner facing surface of
the platforms during rotation of the blade assembly about the longitudinal
axis, and each damper having a lateral edge with a radius of curvature
R.sub.2.
wherein rotation of the blade assembly urges the damper radially outward
and into engagement with the radially inward facing surface of the
platform, wherein upon sufficient relative lateral movement between the
damper and the adjacent pressure side neck the damper engages the lateral
surface of the gusset, and wherein R.sub.1 >R.sub.2 such that engagement
of the damper with the gusset during rotation of the blade assembly
encourages the damper to move radially outward and laterally away from the
pressure side neck surface.
2. The blade assembly according to claim 1, wherein each of the gussets
further includes a nub extending laterally from the gusset, the nub
adapted to engage one of the dampers to axially retain the damper.
3. The blade assembly according to claim 2, wherein the platform includes
linearly extending, parallel lateral edges, and wherein the pressure
surface side of the neck and the radially inward facing surface of the
platform an angle .alpha., and wherein .alpha.<90.degree..
4. The blade assembly according to claim 1, wherein the platform includes
linearly extending, parallel lateral edges.
5. The blade assembly according to claim 1, wherein the pressure surface
side of the neck and the radially inward facing surface of the platform
form an angle .alpha., and wherein .alpha.<90.degree..
6. A rotor blade for an axial flow gas turbine engine, the turbine engine
having an annular flowpath disposed about a longitudinal axis and
including a rotor assembly, the rotor assembly including a plurality of
the rotor blades and a plurality of dampers, the plurality of rotor blades
circumferentially spaced about the longitudinal axis, each of the dampers
disposed between adjacent rotor blades and having a lateral edge with a
radius of curvature R.sub.2, the rotor blade including:
an airfoil portion, a platform, and a root portion, the airfoil portion
extending through the flow path and having a pressure surface and a
suction surface, a platform disposed radially inward of the airfoil
portion, extending laterally about the blade, and including a radially
inward facing surface, the root portion disposed radially inward of the
platform, the root portion having a neck disposed at the radially outward
end of the root portion, the neck including a pressure surface side and a
pair of gussets axially spaced and extending from the pressure surface
side of the neck, each gusset extending from the neck to the radially
inward facing surface of the platform and having a lateral surface with a
radius of curvature R.sub.1 at the juncture of the gusset and the
platform, the gussets providing radial support of the pressure side
platform during rotation of the blade assembly; and
wherein rotation of the blade assembly urges the damper radially outward
and into engagement with the radially inward facing surface of the
platform, wherein upon sufficient relative lateral movement between the
damper and the pressure surface side of the neck, the damper engages the
lateral surface of the gusset, and wherein R.sub.1 >R.sub.2 such that
engagement of the damper with the gusset during rotation of the blade
assembly encourages the damper to move radially outward and laterally away
from the pressure side surface of the neck.
7. The rotor blade according to claim 6, wherein each of the gussets
further includes a nub extending laterally from the gusset, the nub
adapted to engage one of the dampers to axially retain the damper.
8. The rotor blade according to claim 7, wherein the platform includes
linearly extending parallel lateral edges, and wherein the pressure
surface side of the neck and the radially inward facing surface of the
platform an angle .alpha., and wherein .alpha.<90.degree..
9. The rotor blade according to claim 6, wherein the platform includes
linearly extending, parallel lateral edges.
10. The rotor blade according to claim 6, wherein the pressure surface side
of the neck and the radially inward facing surface of the platform form an
angle .alpha., and wherein .alpha.<90.degree..
Description
DESCRIPTION
1. Technical Field
This invention relates to gas turbine engines, and more particularly to a
rotor assembly including a damper between adjacent rotor blades.
2. Background of the Invention
A typical gas turbine engine has an annular, axially extending flow path
for conducting working fluid sequentially through a compressor section, a
combustion section, and a turbine section. The compressor section includes
a plurality of rotating blades which add energy to the working fluid. The
working fluid exits the compressor section and enters the combustion
section. Fuel is mixed with the compressed working fluid and the mixture
is ignited to thereby add more energy to the working fluid. The resulting
products of combustion are then expanded through the turbine section. The
turbine section includes another plurality of rotating blades which
extract energy from the expanding fluid. A portion of this extracted
energy is transferred back to the compressor section via a rotor shaft
interconnecting the compressor section and turbine section. The remainder
of the energy extracted may be used for other functions.
The rotor blades of the compressor section and the turbine section are
included within a rotor assembly of the gas turbine engine. The rotor
assembly includes the rotor shaft and a plurality of rotating disks. The
disks include attachment means for the rotor blades. Rotational forces
during operation of the gas turbine engine cause significant stress within
the structure of the rotor assembly. To accommodate such forces,
sufficient radial support must be provided for all the rotating parts.
This type of support, however, typically increases the bulk of the engine
and thereby lowers operating efficiency of the engine.
Each of the rotor blades includes an airfoil portion, a platform, and a
root portion. The airfoil portion extends through the flow path and
interacts with working fluid to transfer energy between the rotor blade
and working fluid. The platform typically extends laterally from the rotor
blade and is disposed radially between the airfoil portion and the root
portion. The platform includes a radially outward facing flow surface. The
plurality of platforms extends circumferentially about the longitudinal
axis of the gas turbine engine to define a radially inner flow surface for
working fluid. This inner flow surface confines working fluid to the
airfoil portion of the rotor blade. The root portion engages the
attachment means of the disk.
Platforms are generally of two types. The first is a chevron type which
includes lateral edges curved to approximate the airfoil shape of the
rotor blade. This type of shape minimizes the lateral extension of the
platform from the rotor blade. Minimizing the lateral extension or
cantilevered portion of the platform minimizes the bending stress in the
platform caused by rotational forces.
The second type of platform includes parallel lateral edges which extend
linearly. Parallel edges provide for ease of manufacture and ease of
assembly of the rotor blades into the disk. This type of platform,
however, has higher bending stress than a comparable chevron platform due
to the larger lateral extension. The bending stress is particularly
significant in the region of the attachment of the platform to the root
portion and airfoil portion of the rotor blade. To accommodate this
stress, the parallel edged platform is typically made thicker, in the
radial dimension, with a lateral taper towards the lateral edges.
Increasing the thickness of the platform adds to the bulk of the blade.
Another concern is the vibrational energy within the rotor assembly.
Vibrational energy may be destructive and shorten the expected life of
various components associated with the gas turbine engine. A source of
much of the vibrational energy is the interaction of the rotor blades with
the working fluid. A solution to this is to provide a damper in contact
with each blade to reduce the vibrational energy within the rotor blade.
A typical damper is positioned between adjacent rotor blades and engaged
with the underside of adjacent platforms. One such damper is disclosed in
U.S. Pat. No. 4,455,122, issued to Schwarzmann et al, entitled "Blade to
Blade Vibration Damper". The damper disclosed is centrifugally urged
against the underside of adjacent platforms during rotation of the rotor
blades.
Another such damper is disclosed in U.S. Pat. No. 4,457,668, issued to
Hallinger, entitled "Gas Turbine Stages of Turbojets with Devices for the
Air Cooling of the Turbine Wheel Disc". The damper disclosed is sized and
shaped to extend across the passage between rotor blades. The damper
includes a back shaped to conform to the underside of the adjacent
platforms such that the damper is axially retained by engagement with the
platform.
A drawback to both disclosed dampers is that the dampers are not prevented
from engaging the root portion of the rotor blade. Engagement between the
root portion and the damper may lead to detrimental wearing of both the
root portion and the damper. This is especially significant for rotor
blades having a high degree of radial twist such that the root portion and
platform form an acute angle along one side. The surface of the root
portion along that acute angled side is subject to a greater likelihood of
damaging contact.
The above art notwithstanding, scientists and engineers under the direction
of Applicants' Assignee are working to develop dampened rotor blade
assemblies which are easy to assemble, lightweight, and durable.
DISCLOSURE OF THE INVENTION
According to the present invention, a rotor blade includes a gusset
extending radially and laterally between a root portion and a platform,
the gusset providing radial support for a platform and including a
radiused laterally outer edge adapted to urge a damper away from the root
portion.
According to a specific embodiment of the invention, a rotor blade assembly
includes a plurality of circumferentially spaced rotor blades and a
plurality of dampers located between adjacent rotor blades. Each rotor
blade includes an airfoil portion, a root portion, a platform disposed
radially therebetween, and a pair of axially spaced gussets extending
radially and laterally between the root portion and the platform. Each
gusset provides radial support for the platform and includes a radiused
laterally outer edge adapted to urge the damper radially outward and away
from the root portion. Each gusset further includes a nub which extends
laterally and is engaged with the damper to axially retain the damper.
A principle feature of the present invention is the gusset extending
between the root portion and the platform. Another feature is the curved,
laterally outward facing surface of the gusset. A feature of a specific
embodiment is the axial spacing of the pair of gussets and the nub
extending laterally form each gusset.
A primary advantage of the present invention is the ease of assembly of the
rotor assembly as a result of the radial support provided the platform by
the gusset. The gusset permits the use of platforms having parallel
lateral edges by providing radial support to react the bending moment
within the platform resulting from rotation of the rotor assembly. Another
advantage of the present invention is the elimination of degrading wear
between the damper and the root portion as a result of the standoff and
damper positioning provided by the gusset. The gussets extend from the
root portion to prevent contact between the damper and root portion due to
lateral movement of the damper. In addition, the gusset includes a
radiused surface facing the damper to urge the damper radially outward and
laterally away from the root portion during rotation of the rotor
assembly. The radiused surface encourages the damper to remain in a
position extending between adjacent platforms. An advantage of the
particular embodiment is the maintenance of proper axial positioning of
the damper as a result of the pair of nubs extending from the gussets and
retainingly engaged with the damper.
The foregoing and other objects, features and advantages of the present
invention become more apparent in light of the following detailed
description of the exemplary embodiments thereof, as illustrated in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional side view of a gas turbine engine.
FIG. 2 is a partially sectioned side view of a rotor assembly and a damper.
FIG. 3 is a sectional, axial view of a rotor assembly showing a rotor blade
having a gusset, and showing the damper and a damper cavity between
adjacent rotor blades.
FIG. 4 is a perspective view of the rotor blade showing the pair of gussets
with nubs extending laterally.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 illustrates a gas turbine engine 12 having an axially oriented flow
path 14 disposed about a longitudinal axis 16 and including a compressor
18, a combustor 22, and a turbine 24. The compressor includes a rotor
assembly 26 including a plurality of rotating disks 28, each disk having a
plurality of circumferentially spaced blades 32 extending therefrom, and a
stator assembly 34 including a plurality of vanes 36 extending through the
flow path. The compressor blades are engaged with working fluid flowing
through the flow path to transfer energy to the working fluid. The working
fluid exits the compressor and enters the combustor where it is mixed with
fuel and ignited. The products of combustion are expanded through the
turbine. The turbine includes a turbine rotor assembly 38 including a
plurality of disks 42, each disk including a plurality of
circumferentially spaced blades 44 extending through the flow path, and a
stator assembly 46 including a plurality of vanes 48 extending through the
flow path. The turbine rotor blades are engaged with the expanding
products of combustion to transfer energy from the working fluid to the
blades. A portion of this energy is then transferred to the compressor via
a pair of rotor shafts 52,54 interconnecting the turbine and compressor.
In this way a portion of the energy transferred to the turbine is used to
compress incoming working fluid.
Referring now to FIGS. 2 and 3, a portion of the turbine rotor assembly is
shown. The disk includes an attachment means 56 for securing each of the
turbine rotor blades to the disk. As shown in FIG. 3, the attachment means
is comprised of a standard fir tree type retention engaged with each of
the blades. Each of the blades includes an airfoil portion 62, a platform
64, and a root portion 66. The airfoil portion extends radially through
the flow path and includes a pressure surface 68 and a suction surface 72.
The root portion is engaged with the attachment means to secure the blade
to the disk. The platform is located radially between the airfoil portion
and the root portion and extends laterally about the blade. The platform
includes a radially outer surface 74, which, in conjunction with the outer
surfaces of the other platforms defines a flow surface for the working
fluid, and a radially inner surface 76.
An axially spaced pair of gussets 78,82 extend between the pressure surface
side of the neck 83 and the radially inner surface 76 of the platform.
Each gusset includes a laterally projecting nub 84,86 which is engaged
with a damper 88 to provide means of axial retention for the damper. The
suction surface side of the neck 92 also includes an axially spaced pair
of nubs 94 which extend directly from the neck. The four nubs in
conjunction provide both axial retention and radial support to t he damper
within the damper cavity 98.
The gussets as shown in FIGS. 2-4 extend from the pressure surface side of
the neck to approximately the lateral mid point of the pressure surface
side of the platform. The pair of gussets provide radial support for the
cantilevered platform. The gussets include a lateral edge which is
radiused near the junction with the platform. The radius of the lateral
edge R.sub.1 is greater than the corresponding radius R.sub.2 of the outer
corner of the damper. The outer corner of the damper may engage the
lateral edge of the gusset upon sufficient lateral movement of the damper
within the damper cavity. The distance between the lateral edge and the
root portion provides a stand-off to prevent contact between the damper
and the pressure surface side of the root portion. Without the gusset,
contact between the side of the damper and the pressure surface side of
the root portion may occur because of the acute angle .alpha. formed
between the platform and the root portion. The radius R.sub.3 at the
juncture will not prevent such contact.
During operation, rotation of the rotor assembly generates rotational
forces which urge the damper radially outward to engage the adjacent
platforms. Engagement between the damper and the adjacent platforms
reduces the level of vibrational energy within the rotor blades. For
maximum effectiveness of the damper, the damper must be properly located
against the underside of the platforms. If the damper moves laterally
towards the pressure surface side of the adjacent blade, the outer edge of
the damper will engage of the lateral edge of the gussets. Due to the
larger radius of the lateral edge relative of the radius of the outer edge
of the damper, engagement of the damper with the gussets in conjunction
with the rotational forces will urge the damper laterally away from the
pressure surface of the blade and thereby provide damper positioning
means. This prevents the damper from rubbing against the neck of the blade
and degrading the damper end or the neck portion of the blade. If the
damper moves laterally away from the pressure side neck portion and
towards the suction side neck, the juncture between the suction side neck
and the platform is also radiused and has a radius R.sub.4 greater than
the radius of the adjacent outer edge of the damper. The combination of
the rotational force and the radius of the juncture between the suction
side neck and the platform wall urge the damper to move laterally away
from the suction surface side. In addition, the obtuse angle .beta. formed
between the suction surface side and the platform will block contact.
To prevent the damper from becoming misaligned axially the nubs provide
means to axially retain the damper. As shown in FIGS. 2 and 3, the nubs
extends radially under and between the upstream end and the downstream end
of the damper. The nubs provide a loose retention of the damper such that
during rotation of the rotor assembly there should little or no contact
between the damper and the nubs. During a non-operational condition of the
gas turbine engine the nubs provide radial support for the damper. In
addition, the nubs confine the damper to a limited space such that the
damper may not rotate about a longitudinal axis and become misaligned
within the damper cavity.
Although shown as a turbine rotor blade, it should be understood by those
skilled in the art that the present invention has applicability to other
rotor blades, such as compressor rotor blades. Additionally, it should be
apparent to those skilled in the art that different quantities of gussets
may be used as desired.
Although the invention has been shown and described with respect with
exemplary embodiments thereof, it should be understood by those skilled in
the art that various changes, omissions, and additions may be made
thereto, without departing from the spirit and scope of the invention.
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